Assays can be procedures for determining the presence, quantity, activity, and/or other properties or characteristics of components in a sample. In some cases, the samples to be assayed are complex, the components of interest within the samples—e.g., a nucleic acid, an enzyme, a virus, a bacterium—are only minor constituents of the samples, and the results of the assays are required quickly and/or for many samples.
Some current systems perform assays with the aid of droplets generated in drop generators. Often, the droplet generators work by partitioning a sample into multiple droplets. The sample may be an aqueous sample that is contacted with a stream of oil fluid in such a way as to form a disperse phase of aqueous droplets in a continuous oil phase. In such systems, droplets with sample partitions may be generated for storage in a droplet storage vessel, in which sample can subsequently be processed (e.g., amplified in the case of PCR) and analyzed. Droplets may then be detected such as by being introduced into a droplet reader. Improved droplet detection mechanisms would be of great benefit to biological and clinical assays that use droplet-based assays.